It has long been recognized that the efficiency and fuel economy of an internal combustion engine can be improved by preheating the fuel supplied to the carburetor. Fuel preheating can be accomplished by passing the fuel enroute to the carburetor in heat exchange relationship with engine coolant. Prior art fuel preheaters are shown by way of example in Dunnam U.S. Pat. No. 4,091,782, Rabbiosi U.S. Pat. No. 3,986,486 and DeShaies U.S. Pat. No. 3,253,647.
My copending application Ser. No. 347,348 entitled Fuel Preheater discloses a fuel preheater which is adapted for use with an engine coolant system which includes a coolant conduit through which coolant can flow and a fuel conduit for supplying fuel from a fuel supply to the engine. The preheater of my copening application includes a coolant tube and a fuel tube with a portion of the fuel tube forming a coil extending around the exterior of the coolant tube in heat exchange relationship therewith.
One problem with prior art fuel preheaters is that they tend to produce vapor lock under at least some operating conditions. Thus, vapor lock is more likely to occur, for example, on high compression engines or on engines operating in hot desert climates.